The invention is generally related to the field of semiconductor processing and more specifically to hardmasks for etching hard-to-etch materials in a semiconductor process.
Many materials, such as Pt, Ir, Ru, IrO2, RuO2, BST (Barium-strontium-titanate), PZT (Lead Zirconate Titanate), SBT (Bismuth Strontium Tantalunate), FeNi, FeNiCo, and others used in making DRAMs, FeRAMs (ferroelectric random access memories), or magnetic storage devices, are very difficult to etch due to the lack of volatile etch by products under normal plasma etch conditions. The etch of these materials is typically accomplished by physical sputtering or chemically assisted sputtering. As a result, photoresist, silicon oxide, or silicon nitride masks do not offer enough etch selectivity. Therefore, masking for these etches is very difficult.
One masking approach uses a TiAlN based hardmask. Under the proper etch conditions, TiAlN and TiN have enough selectivity to serve as a hardmask when etching these hard-to-etch materials. The proper etch conditions include a gas mixture of oxygen and Cl- or F-bearing gases at specific concentrations. The restrictions on the etch conditions imposed by the hardmask limit the process window and process optimizations. Furthermore, removing the TiAlN hardmask has a tendency to etch the capacitor dielectric and bottom barrier materials.
The invention uses a carbon hardmask for etching hard-to-etch materials such as Pt, Ir, Ru, IrO2, RuO2, BST (Barium-strontium-titanate), PZT (Lead Zirconate Titanate), SBT (Bismuth Strontium Tantalunate), FeNi, and FeNiCo.
An advantage of the invention is providing a hardmask for etching hard-to-etch materials that expands the process chemistries available for etching the hard-to-etch materials.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.